You can't. Only i5 and i7 can OC. Normal ones can OC 400mhz and i5 3570k and i7 3770k are unlocked and can OC as far as you are willing to try.

nuff said. Besides that, you'll want the extra horsepower for the VMs. On that note, if you plan on running more than one VM 24/7, it's probably worth buying 16GB of RAM. It's still pretty cheap and you only really need 1600mhz.